Acyclic Analogues of Deoxyadenosine 3',5'-Bisphosphates as P2Y1

Maqbool A. Siddiqui, Pamela Russ, Victor E. Marquez, Roger Busson, Piet Herdewijn, ... José L Boyer , Mary Adams , R Gnana Ravi , Kenneth A Jacob...
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Acyclic Analogues of Deoxyadenosine 3′,5′-Bisphosphates as P2Y1 Receptor Antagonists Yong-Chul Kim,† Carola Gallo-Rodriguez,†,§ Soo-Yeon Jang,† Erathodiyil Nandanan,† Mary Adams,‡ T. Kendall Harden,‡ Jose´ L. Boyer,‡ and Kenneth A. Jacobson*,† Molecular Recognition Section, Laboratory of Bioorganic Chemistry, National Institute of Diabetes, Digestive and Kidney Diseases, National Institutes of Health, Bethesda, Maryland 20892-0810, Department of Pharmacology, University of North Carolina, School of Medicine, Chapel Hill, North Carolina 27599-7365, and CIHIDECAR, Departamento de Quimica Organica, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires, Ciudad Universitaria, Pabellon II, 1428 Buenos Aires, Argentina Received October 18, 1999

P2Y1 receptors are activated by ADP and occur on endothelial cells, smooth muscle, epithelial cells, lungs, pancreas, platelets, and in the central nervous system. With the aid of molecular modeling, we have designed nucleotide analogues that act as selective antagonists at this subtype. The present study has tested the hypothesis that acyclic modifications of the ribose ring, proven highly successful for nucleoside antiviral agents such as gancyclovir, are generalizable to P2Y receptor ligands. Specifically, the binding site of the P2Y1 receptor was found to be sufficiently accommodating to allow the substitution of the ribose group with acyclic aliphatic and aromatic chains attached to the 9-position of adenine. Three groups of adenine derivatives having diverse side-chain structures, each containing two symmetrical phosphate or phosphonate groups, were prepared. Biological activity was demonstrated by the ability of the acyclic derivatives to act as agonists or antagonists in the stimulation of phospholipase C in turkey erythrocyte membranes. An acyclic N6-methyladenine derivative, 2-[2-(6-methylaminopurin-9-yl)-ethyl]-propane-1,3-bisoxy(diammoniumphosphate) (10), containing an isopentyl bisphosphate moiety, was a full antagonist at the P2Y1 receptor with an IC50 value of 1.60 µM. The corresponding 2-Cl derivative (11) was even more potent with an IC50 value of 0.84 µM. Homologation of the ethylene group at the 9-position to 3-5 methylene units or inclusion of cis- or trans-olefinic groups greatly reduced antagonist potency at the P2Y1 receptor. Analogues containing a diethanolamine amide group and an aryl di(methylphosphonate) were both less potent than 10 as antagonists, with IC50 values of 14 and 16 µM, respectively, and no agonist activity was observed for these analogues. Thus, the ribose moiety is clearly not essential for recognition by the turkey P2Y1 receptor, although a cyclic structure appears to be important for receptor activation, and the acyclic approach to the design of P2 receptor antagonists is valid. Introduction P2 receptors, which are activated by purine and/or pyrimidine nucleotides, consist of two families: G protein-coupled receptors termed P2Y, of which five mammalian subtypes have been cloned, and ligandgated cation channels termed P2X, of which seven mammalian subtypes have been cloned.1,2 The nomenclature of P2 receptors and their various ligand specificities has been reviewed.2-5 The chick brain P2Y1 receptor was the first P2 subtype to be cloned.6 Subsequently, P2Y1 receptors have been cloned from human, cow, turkey, rat, and mouse.7,8 P2Y1 receptors occur on endothelial cells,9 smooth muscle,9 epithelial cells,10 lungs,10 platelets,11 pancreas,12 and in the central nervous system.13 The role of this receptor in vivo is * Correspondence to: Dr. Kenneth A. Jacobson, Chief, Molecular Recognition Section, Bldg. 8A, Rm. B1A-19, NIH, NIDDK, LBC, Bethesda, MD 20892-0810. Tel.: (301) 496-9024. Fax: (301) 480-8422. E-mail: [email protected]. † National Institutes of Health. ‡ University of North Carolina, School of Medicine. § Universidad de Buenos Aires.

largely unknown, and few pharmacological probes are available. Thus, the development of selective P2Y1 receptor agonists and antagonists of high affinity is a critical need. Boyer et al. in 199614 reported that various naturally occurring bisphosphates of adenosine (e.g. adenosine 3′,5′-bisphosphate, A3P5P) act as competitive antagonists of this subtype. Synthetic modifications which have increased the potency and selectivity of the bisphosphate derivatives include N6-methyl (e.g. 3, 4, 6, and 7), 2-chloro (e.g. 4 and 7), 2-deoxy (e.g. 2-7), and the carbocyclic analogue of ribose (e.g. 5-7) (Figure 1).15-18 Compound 3 (MRS 2179) has a KB value at human P2Y1 receptors of 100 nM and does not interact with other P2 receptor subtypes at that concentration.16 Molecular modeling of nucleotides docked in the putative, principal binding site of the P2Y1 receptor18,19 suggests that neither the ring oxygen atom nor 2′- and 3′-oxygens of the ribose moiety are involved in specific stabilizing interactions, such as H-bonding, with the receptor. Using this structural insight, we have designed modified ribose analogues including deoxy-,15,17 carbocy-

10.1021/jm9905211 CCC: $19.00 © 2000 American Chemical Society Published on Web 02/09/2000

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ments surrounding the ribose moiety in P2Y1 receptor ligands provide latitude of modification. The present study introduces a more radical departure from the ribose ring structure than in the previous work,18 i.e. acyclic aliphatic chains and a pendant aromatic ring. For nucleosides that act as antiviral agents, among the most effective modifications are the acyclic ribose modifications.20-22 Such aglycosyl antiviral nucleosides include acyclovir and gancyclovir, 1, in which a 2-methylbutyl group can be considered to overlay the ribose ring. Analogues based on the design concept of gancyclovir, although more flexible, may still adopt the receptor-preferred conformation of the ribose or cyclopentyl rings. We wished to test the hypothesis that this approach, found successful for antiviral nucleosides, is generalizable to P2 receptor ligands. Are the steric requirements of the binding site of the P2Y1 receptor, in which specific cationic amino acid side chains form putative electrostatic bonds to either triphosphate or bisphosphate groups,19 sufficiently permissive to allow the substitution of ribose with highly flexible acyclic substitutions? Figure 1. Structures of acyclic nucleotide analogues synthesized as ligands for the P2Y1 receptor. The corresponding ammonium salts were synthesized and tested for biological activity.

clic,17 and methanocarba-18 modifications, which proved to retain receptor affinity. Thus, the structural require-

Results Chemical Synthesis. Acyclic analogues similar in concept to gancyclovir21 were synthesized as shown in Scheme 1.22 The analogues, 8-11, contained a branched aliphatic (isopentyl) group, and the only differences

Scheme 1. Synthesis of 9-Isopentyladenine Nucleotide Derivativesa

a Reagents: (i) NaOEt, ether, 0 °C to RT, 30 min, 85%; (ii) 1,2-dibromoethane, DMF, 90 °C, 10 h, 92%; (iii) adenine analogue, K CO , 2 3 DMF, 65 °C, 24 h; (iv) NaOMe, methanol, RT to 15 °C, 50∼80% for two steps; (v) NaBH4, CH2Cl2:MeOH (3:2), RT, 4-6 h, 74-98%; (vi) DBPP, LDA, THF, -78 °C to RT, 4 h, 24-78%; (vii) H2/Pd-C, MeOH:H2O (1:1), RT, 1 atm, 37-88%; (viii) BCl3, anisole, CH2Cl2, -78 °C, 1 h, 0 °C, 48 h, 54-62%.

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Scheme 2. Synthesis of Acyclic Nucleotide Derivatives Containing Groups Larger than Isopentyl at the Adenine 9-Positiona

lation of inositol phosphate accumulation in membranes isolated from [3H]inositol-labeled turkey erythrocytes. As in our previous studies,15-19 the bisphosphate analogues prepared in the present study were tested separately for agonist and antagonist activity in the PLC assay at the P2Y1 receptor in turkey erythrocyte membranes, and the results are reported in Table 2. Concentration-response curves were obtained for each compound alone and in combination with the agonist 2-MeSADP (10 nM). Concentration-response curves for representative compounds, 11, 17, and 18, are shown in Figure 2. An acyclic N6-methyladenine derivative, 10, containing a symmetric isopentyl bisphosphate moiety was a P2Y1 receptor antagonist with an IC50 value of 1.60 µM. The unsubstituted adenine derivative, 8, displayed only weak antagonist properties, and the 2-chloro-substituted derivative, 9, was somewhat more potent. The corresponding 2-chloro-N6-methyl derivative, 11, was even more potent with an IC50 value of 0.84 µM. Homologation of the ethylene group of 10 at the 9-position to 3-5 methylene units or inclusion of cis- or transolefinic groups, i.e. compounds 12-16, greatly reduced antagonist potency at the P2Y1 receptor. None of the aliphatic acyclic derivatives, 8-16, displayed agonist activity. Analogues containing a diethanolamine amide group, 17, and an aryl di(methylphosphonate), 18, were both less potent than 11 as antagonists, with IC50 values of 14 and 16 µM, respectively, and no agonist activity was observed for these analogues.

a Reagents: (i) 30a: 1,3-diiodopropane; 30b: 1,4-dibromobutane; 30c: 1,5-dibromopentane; 30d: cis-1,4-dichloro-2-butene; 30e: trans-1,4-dibromo-2-butene; 1:1 DMF:toluene, ∆; (ii) N6methyladenine, K2CO3, DMF, ∆; (iii) NaOMe, methanol, RT; (iv) NaBH4, CH2Cl2:MeOH, RT; (v) DBPP, LDA, THF, -78 °C to RT, 16 h; (vi) 12, 13, 14: H2/10% Pd-C, MeOH, RT, 3 atm; 15, 16: BCl3, CH2Cl2, 5 °C.

Discussion present were in the substitution pattern of the adenine moiety. The N6-methyl and 2-chloro modifications of adenine have been included, due to the anticipated enhancement of affinity (2-Cl versus 2-H) and perturbation of the relative degree of agonist and antagonist character, with the N6-methyl group expected to minimize agonist effects. In the previous study, methyl substitution of the exocyclic amino group tended to convert partial agonists into pure antagonists. The ethylene group of 10 at the 9-position of adenine was homologated (Scheme 2) to propyl, 12, butyl, 13, and pentyl, 14, and to cis- and trans-butenyl, 15 and 16. Furthermore, several amide-containing groups were incorporated through a carboxymethyl group at the 9-position of the adenine (Scheme 3), including a diethanolamine derivative, 17, and an aniline 3,5-di(methylphosphonate), 18. All three of these sets of analogues contained symmetrical bisphosphate (or phosphonate) moieties. Characterizations by high-resolution mass spectrometry, HPLC in two different solvent systems, and the yields of phosphorylation of each compound tested are summarized in Table 1. Biological Activity. Adenine nucleotides markedly stimulate inositol lipid hydrolysis by phospholipase C in turkey erythrocyte membranes,23 through activation of a P2Y1 receptor.24 The 5′-diphosphate standard used in screening these analogues, 2-methylthioadenosine5′-diphosphate (2-MeSADP), has a higher agonist potency than the corresponding triphosphate26 for stimu-

The present study has identified new pharmacological probes of P2Y1 receptors that are to be considered adenine derivatives containing a negatively charged aglycosyl side chain, rather than nucleoside analogues. Thus, the ribose moiety is clearly not essential for recognition by the turkey P2Y1 receptor, although a cyclic structure appears to be important for receptor activation. Unlike the corresponding ribose series,17,18 the two isopentyl analogues, 8 and 9, which contained an unsubstituted exocyclic amino group displayed no agonist properties. Therefore, the acyclic approach to the design of P2 receptor antagonists is valid, and three highly divergent lead structural classes (gancyclovirtype alkyl chain and homologues, 8-16, alkyl amide, 17, and aryl amide, 18) have been presented. In a recently published study, which also indicates that an intact ribose moiety is not critical for interaction with P2 receptors, various chain-substituted xanthine derivatives were found to interact as antagonists with cardiac P2X receptors.27 In these derivatives short alkyl groups replaced the ribose moiety of hypothetical xanthosine nucleotide structures. Specifically, for the P2Y1 receptor, we have proposed, based on molecular modeling, that there are no required hydrogen bonds between the receptor and the ribose ring oxygen of a bound nucleotide ligand. This prediction was supported by the synthesis of highly potent carbocyclic bisphosphate analogues.17,18 While in the previous study of ribose derivatives the addition of a methyl group to the exocyclic amine tended

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Scheme 3. Synthesis of Acyclic Nucleotide Derivatives Containing an Amide Bonda

a Reagents: (i) (Ph) P, CBr , 25 °C, 12 h, 52%; (ii) P(OCH ) , 80 °C, 6 h, 94%; (iii) Pd/C, H , 25 °C, 1 h, 100%; (iv) NaH, BrCH COOEt, 3 4 3 3 2 2 25 °C, 12 h, 82%; (v) 1 N NaOH, 25 °C, 1 h, 83%; (vi) 4-nitrophenol, EDAC, DMAP, 25 °C, 2 h, HN(CH2CH2OH)2, 25 °C, 12 h, 36%; (vii) LDA, tetrabenzylpyrophosphate, -78 °C, 0.5 h, 0 °C, 2 h, 94%; (viii) BCl3, anisole, -78 °C, 1 h, 0 °C, 4 h, 28%; (ix) 38, EDAC, 25 °C, 12 h, 82%; (x) TMS-Br, 25 °C, 12 h, 45%.

Table 1. Synthetic Data for Nucleotide Derivatives, Including Structural Verification Using High-Resolution Mass Spectroscopy and Purity Verification Using HPLC HPLC (rt; min)a FAB (M - H+) no.

formula

calcd

found

system A

system B

yield (%)b

8 9 10 11 12 13 14 15 16 17 18

C10H17O8N5P2 C10H16ClO8N5P2 C11H19O8N5P2 C11H18ClO8N5P2 C12H20O8N5P2 C13H22O8N5P2 C14H24O8N5P2 C13H20O8N5P2 C13H20O8N5P2 C12H19ClO9N6P2 C16H19ClO7N6P2

398.0631 432.0241 410.0631 446.0397 424.0787 438.0944 452.1100 436.0787 436.0787 487.0290 503.0401

398.0592 432.0237 410.0630 446.0410 424.0786 438.0959 452.1101 436.0797 436.0770 487.0299 503.0388

2.68 2.70 5.48 5.63 4.81 5.26 5.78 4.97 4.55 6.80 8.28

8.49 10.18 5.90 10.26 9.82 8.62 8.97 9.03 8.81 9.55 10.39

21.1 14.9 48.4 42.1 9.9 14.0 11.3 7.5 6.6 27.3

a Purity of each derivative was g95%, as determined using HPLC with two different mobile phases. System A: gradient of 0.1 M TEAA/CH3CN from 95/5 to 40/60. System B: gradient of 5 mM TBAP/CH3CN from 80/20 to 40/60. b The percent yields refer to overall yield for each phosphorylation sequence.

to convert partial agonists into full antagonists, in the present study only antagonism of P2Y1 receptor-mediated effects was observed. The highest affinity among the three novel structures of the present study occurred with the 2-chloro-N6-methyl gancyclovir equivalent, i.e.

compound 11. Although further structural refinement would be desirable to optimize affinity, the affinities of these analogues are comparable to recently synthesized, moderately potent antagonists of the P2Y1 receptor, based on ribose.17,18 Although the lead bisphosphate structures, upon which these analogues are based, i.e. 2-7, are selective for the P2Y1 subtype, it will nevertheless be useful to examine the acyclic compounds as agonists and/or antagonists at other subtypes of P2 receptors. The phosphonate group was included in 18 as a potentially more stable alternative to phosphate that would preserve the required negative charges. In the previous study, a 5′-O-phosphonylmethyl analogue of ribose was found to interact with P2Y1 receptors,17 although it was 4-fold less potent than the corresponding bisphosphate but with the same ratio of agonist/ antagonist properties. The present structural leads may prove useful in the search for other phosphate group substitutes. The moderately potent P2Y1 receptor antagonists found in the present study, principally 11, now require characterization at other P2 receptor subtypes. Compound 11 (10 µm) was recently shown to be inactive as either agonist or antagonist at rat P2X1 receptors expressed in Xenopus oocytes.30 If proven selective for

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Table 2. In Vitro Pharmacological Data for Stimulation of PLC at Turkey Erythrocyte P2Y1 Receptors (Agonist Effect) and the Inhibition of PLC Stimulation Elicited by 30 nM 2-MeSADP (Antagonist Effect), for at Least Three Separate Determinations agonist effect, % of maximal compd increasea 2c 3c 4c 5c 6c,e 7c 8 9 10e 11e 12 13 14 15 16 17 18

12 ( 3 NE NE 27 ( 11 NE NE NE NE NE NE NE NE NE NE NE NE NE

EC50, µMa 6.29 ( 2.54 7.21 ( 4.40

antagonist effect, % of maximal inhibitionb

IC50, µMb (n)

87 ( 4 99 ( 1 95 ( 1 73 ( 11 99 ( 1 95 ( 1 63 ( 7d 94 ( 2 100 99 ( 1 68 ( 4d 65 ( 6d 56 ( 2d 77 ( 3d 54 ( 6d 89 ( 3d 94 ( 2d

5.76 ( 0.68 0.331 ( 0.059 0.206 ( 0.053 2.53 ( 0.57 0.331 ( 0.059 (5) 0.206 ( 0.053 >50 7.57 ( 1.41 (5) 1.60 ( 0.47 0.840 ( 0.130 >30 >50 ∼100 >50 ∼100 14.0 ( 6.0 (4) 15.5 ( 4.2

a Agonist potencies were calculated using a four-parameter logistic equation and the GraphPad softaware package (GraphPad, San Diego, CA). EC50 values (mean ( standard error) represent the concentration at which 50% of the maximal effect is achieved. Relative efficacies (%) were determined by comparison with the effect produced by a maximal effective concentration of 2-MeSADP in the same experiment. Small increase refers to 98%) in solvent system A, 10.26 min in system B. 2-[3-(6-Methylamino-purin-9-yl)-propyl]-propane-1,3bisoxy(diammoniumphosphate) (12). Starting from 9 mg of 34a (0.0114 mmol) with the same procedure shown in the preparation of 8, 2.6 mg 12 was obtained (45%). 1H NMR (D2O) 1.37 (2H, m, -CH2-), 1.96 (3H, m, -CH2-, -CH-), 3.12 (3H, bs, N6-CH3), 3.84 (4H, dd, J ) 5.9 Hz, 4.7 Hz, 2×-CH2O-), 4.23 (2H, t, J ) 6.8 Hz, -NCH2-), 8.15, 8.26 (2H, 2s, H-2, H-8). 31P NMR (D2O) -21.06 (s, 1′-P, 3′-P). 2-[4-(6-Methylamino-purin-9-yl)-butyl]-propane-1,3bisoxy(diammoniumphosphate) (13). Starting from 18 mg of 34b (0.0225 mmol) with the same procedure shown in the preparation of 8, 5.1 mg of 13 was obtained (44.5%).1H NMR (D2O) 1.37 (4H, m, CHCH2CH2), 1.86 (3H, m, -CH2-, -CH-), 3.01 (3H, bs, N6-CH3), 3.81 (4H, m, 2CH2OP), 4.23 (2H, t, J ) 6.6 Hz, NCH2), 8.09, 8.22 (2H, 2s, H-2, H-8). 31P NMR (D2O) -20.16 (s, 1′-P, 3′-P). 2-[5-(6-Methylamino-purin-9-yl)-pentyl]-propane-1,3bisoxy(diammoniumphosphate) (14). Starting from 18 mg of 34c (0.0225 mmol) with the same procedure shown in the preparation of 8, 5.4 mg of 14 was obtained (47%). 1H NMR (D2O) 1.30 (4H, m, CHCH2CH2CH2), 1.85 (3H, m, -CH2-, -CH-), 3.08 (3H, bs, N6-CH3), 3.83 (4H, m, 2CH2OP), 4.18 (2H, t, J ) 6.9 Hz, NCH2), 8.05, 8.17 (2H, 2s, H-2, H-8). 31P NMR (D2O) -20.51 (s, 1′-P, 3′-P). 2-[4-(6-Methylamino-purin-9-yl)-cis-but-2-enyl]-propane1,3-bisoxy(diammoniumphosphate) (15). Starting from 18 mg of 34d (0.0226 mmol) with the same procedure shown in the preparation of 9, 5.4 mg of 15 was obtained (47%). 1H NMR (D2O) 2.10 (1H, m, CH), 2.38 (2H, t, J ) 6.9 Hz, CHCH2CHd), 3.15 (3H, bs, N6-CH3), 3.92 (4H, t, J ) 6 Hz, 2CH2OP), 4.93 (2H, d, J ) 5.7 Hz, NCH2), 5.76 (1H, dt, J ) 10.8, 6.9 Hz, CHd), 5.87 (1H, dt, J ) 10.8, 7.8 Hz, CHd), 8.18, 8.23 (2H, 2s, H-2, H-8). 31P NMR (D2O) -20.82 (s, 1′-P, 3′-P). 2-[4-(6-Methylamino-purin-9-yl)-trans-but-2-enyl]-propane-1,3-bisoxy(diammoniumphosphate) (16). Starting from 18 mg of 34e (0.0226 mmol) with the same procedure shown in the preparation of 9, 4.5 mg of 16 was obtained (39%). 1H NMR (D O) 1.99 (1H, m, CH), 2.18 (2H, t, J ) 6.8 Hz, 2 CHCH2CHd), 3.13 (3H, bs, N6-CH3), 3.83 (4H, t, J ) 5.9 Hz, 2CH2OP), 5.76 (1H, dt, J ) 15.6, 6.8 Hz, CHd), 5.87 (1H, dt, J ) 15.6, 5.9 Hz, CHd), 8.13, 8.25 (2H, 2s, H-2, H-8) (NCH2 signal was overlapped with DHO signal), 31P NMR (D2O) -20.79 (s, 1′-P, 3′-P). 9-Bis(2-phosphatoethylamino)-acetyl-2-chloro-6-methylamino-purine Triammonium Monotriethylammonium Salt (17). Starting from 35 mg of 43 (0.041 mmol) using the same procedure shown for the preparation of 9, 6.5 mg of 17 was obtained (29%). 1H NMR (D2O) 3.09 (3H, bs, N6-CH3), 3.65-3.69 (2H, m, CH2), 3.85-3.87 (2H, m, CH2), 3.95-3.98 (2H, m, CH2), 4.10-4.13 (2H, m, CH2), 5.36 (2H, s, -NCH2CO), 8.06 (1H, s, H-8). 31P NMR (D2O) 1.65 (bs). (2-Chloro-6-methylamino-purin-9-yl)-acetaminophenyl3′,5′-bismethylphosphonate Tetraammonium Salt (18). To a solution of 35 mg of 44 (0.062 mmol) in 1 mL of anhydrous CH3CN was added 43 µL of trimethylsilyl bromide (0.31 mmol) at 25 °C under N2 atmosphere. The mixture was stirred for 12 h, and the solvent was removed by N2 stream. The residue was partitioned between ether and 0.5 M ammonium bicarbonate solution, and the water fraction was purified by an ionexchange column chromatography using Sephadex-DEAE A-25 resin with a linear gradient (0.01 to 0.5 M) of 0.5 M ammonium bicarbonate as the mobile phase, and UV and HPLC were used to monitor the elution to give 27 mg of 18 (76%). 1H NMR (D2O) 2.90 (2H, d, J ) 20.5 Hz, -CH2P-), 2.99 (3H, s, -NHCH3), 3.16 (2H, d, J ) 20.5 Hz, -CH2P-), 5.06 (2H, s, -NCH2-), 6.97 (1H, s, Ph), 7.14 (1H, s, Ph), 7.26 (1H, s, Ph), 8.02 (1H, s, H-8) 31P NMR (D2O) 18.61 (t, J ) 20.1 Hz), 19.75 (t, J ) 20.5 Hz): with proton decoupling off mode.

Journal of Medicinal Chemistry, 2000, Vol. 43, No. 4 751 Dimethyl 2-[2-(6-Amino-2-chloro-purin-9-yl)ethyl]malonate (24). A mixture of 0.20 g of 6-amino-2-chloro-purine (1.18 mmol), 0.51 g of 21 (1.5 mmol) and 0.42 g of dry potassium carbonate (3 mmol) in 8 mL of anhydrous DMF was stirred at 60 °C for 24 h. The mixture was filtered and the filtrate evaporated to dryness under reduced pressure to give a crude 22. The crude 22 was dissolved in 5 mL of methanol, and a solution of 54 mg of sodium methoxide in 1 mL of methanol was added with stirring. Stirring was continued for 3 h, during which time a precipitate was formed. The reaction mixture was kept at 0 °C for 30 min, and the white precipitate was collected by filtration and dried under high vacuum to afford 0.31 g of 24 (80%). 1H NMR (CDCl3) 2.48 (2H, q, J ) 6.8 Hz, -CH2-), 3.36 (1H, t, J ) 6.8 Hz, -CH-), 3.75 (6H, s, 2×OCH3), 4.29 (2H, t, J ) 6.8 Hz, -NCH2-), 5.96 (2H, bs, -NH2), 7.79 (1H, s, H-8). MS (EI) (M+) 327. HRMS (EI) Calcd: 327.0734; Found: 327.0723. Dimethyl 2-[2-(2-Chloro-6-methylamino-purin-9-yl)ethyl]malonate (25). Starting from 0.37 g of 2-chloro-6methylamino-purine (2 mmol) and 0.68 g of 21 (2 mmol) with the same procedure shown in the preparation of 24, 0.34 g of 25 was obtained (50%). 1H NMR (CDCl3) 2.47 (2H, q, J ) 6.8 Hz, -CH2-), 3.19 (3H, s, N6-CH3), 3.34 (1H, t, J ) 6.8 Hz, -CH-), 3.75 (6H, s, 2×-OCH3), 4.26 (2H, t, J ) 6.8 Hz, -NCH2-), 5.97 (1H, bs, -NH-), 7.71 (1H, s, H-8). MS (EI) (M+) 341. HRMS (EI) Calcd: 341.0890; Found: 341.0893. 2-Chloro-9-[4-hydroxy-3-(hydroxymethyl)butyl]-6amino-purine (26). To a suspension of 0.30 g of 24 (0.92 mmol) and 0.10 g of sodium borohydride (2.6 mmol) in 1.5 mL of CH2Cl2 was added dropwise 1 mL of MeOH, while maintaining the reaction temperature at 25 °C. The mixture was stirred at 25 °C for 4 h, 1 mL of water was added, and the mixture was neutralized by a dropwise addition of concentrated HCl to pH 7.0 with cooling. The mixture was diluted with MeOH and evaporated three times under vacuum, and the crude residue was purified with a silica gel column chromatography (CHCl3/MeOH ) 10/1) to give 0.19 g of 26 as a white powder (74%). 1H NMR (CD3OD) 1.58-1.68 (1H, m, -CH-), 1.92 (2H, q, J ) 6.8 Hz, -CH2-), 3.52-3.68 (4H, m, 2×CH2OH), 4.30 (t, J ) 6.8 Hz, -NCH2-), 8.12 (1H, s, H-8). MS (EI) 271 (M+). HRMS (EI) Calcd: 271.0836; Found: 271.0828. 2-Chloro-9-[4-hydroxy-3-(hydroxymethyl)butyl]-6methylamino-purine (27). Starting from 0.24 g of 25 (0.72 mmol) with the same procedure shown in the preparation of 26, 0.19 g of 27 was obtained (93%) as a white powder. 1H NMR (DMSO-d6) 1.39-1.47 (1H, m, -CH-), 1.77 (2H, q, J ) 6.8 Hz, -CH2-), 2.91 (3H, d, J ) 4.9 Hz, N6-CH3), 3.30-3.47 (4H, m, 2×-CH2OH), 4.16 (2H, t, J ) 6.8 Hz, -NCH2-), 4.34 (1H, t, J ) 4.9 Hz, -NH-), 8.15 (1H, s, H-8). MS (CI) 286 (M + 1), HRMS (EI) Calcd: 285.0992; Found: 285.0985. 2-[2-(6-Amino-2-chloro-purin-9-yl)-ethyl]-propane-1,3bisoxy(dibenzylphosphate) (28). To a solution of 0.18 g of 26 (0.66 mmol) and 1.43 g of tetrabenzyl pyrophosphate (2.65 mmol) in 10 mL of anhydrous THF was slowly added 1.33 mL of lithium diisopropylamide solution (2.0 M in THF, 2.65 mmol) at -78 °C. After 1 h of stirring, the reaction mixture was warmed to 25 °C and stirred for additional 12 h. A white precipitate, lithium dibenzyl phosphate, was filtered off, and the filtrate was purified with silica gel column chromatography (CHCl3/MeOH ) 80/1) to give 0.13 g of 28 as a colorless oil (24%). 1H NMR(CDCl3) 1.70-1.76 (3H, m, -CH2-, -CH-), 3.843.97 (4H, m, 2×-CH2O-), 4.04 (2H, t, J ) 6.8 Hz, -NCH2-), 4.99 and 5.03 (8H, 2d, J ) 3.9 Hz, 4×-OCH2-), 6.42 (2H, s, -NH2), 7.31 (20H, m, 4×-Ph), 7.68 (1H, s, H-8). 31P NMR (CDCl3) -22.22 (s, 1′-P, 3′-P). MS (FAB+) 792 (M+ + 1). HRMS (FAB-) (M + H) Calcd: 792.2119; Found: 792.2124. 2-[2-(2-Chloro-6-methylamino-purin-9-yl)-ethyl]-propane-1,3-bisoxy(dibenzylphosphate) (29). Starting from 0.05 g of 27 (0.17 mmol) with the same procedure shown in the preparation of 28, 0.11 g of 29 was obtained as a colorless oil (78%). 1H NMR (CDCl3) 1.68-1.75 (3H, m, -CH2-, -CH-), 3.20 (3H, bs, -N6-CH3), 3.83-3.96 (4H, m, 2CH2-O), 4.04 (2H, t, J ) 6.8 Hz, -NCH2-), 4.99 and 5.02 (8H, 2d, J ) 3.9 Hz, 4×-OCH2-), 6.23 (1H, bs, -NH-), 7.32 (20H, m, 4×-Ph), 7.62

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Journal of Medicinal Chemistry, 2000, Vol. 43, No. 4

(1H, s, H-8). 31P NMR (CDCl3) -22.42 (s, 1′-P, 3′-P). MS (FAB) 806 (M+ + 1). HRMS (FAB-) (M + Cs) Calcd: 938.1252; Found: 938.1227. Triethyl 4-Iodobutane-1,1,1-tricarboxylate (30a). To a solution of 2.21 g of sodium triethyl methanetricarboxylate (8.7 mmol) in 1:1 toluene/anhydrous DMF (10 mL) was added 5.15 g of 1,3-diiodopropane (17.4 mmol), and the solution was heated at 60 °C for 5 h, during which time a precipitate was formed. After cooling to room temperature, toluene (50 mL) was added and the mixture was filtered. The filtrate was washed with water (4 × 100 mL), dried (anhydrous Na2SO4), and concentrated under reduced pressure. Silica gel column chromatography eluting with petroleum ether for the removal of excess of diiodopropane and then 10:1 petroleum ether-ethyl acetate afforded 2.52 g of 1 (72%) as a colorless oil. 1H NMR (CDCl3) 1.29 (9H, t, J ) 7.8 Hz, -CH3), 2.05 (2H, m, -CH2-), 2.22 (2H, m, -CH2-), 3.19 (2H, t, J ) 6.6 Hz, -CH2I), 4.27 (6H, q, J ) 6.9 Hz, -OCH2-). MS (FAB+) 401 (M + 1). HRMS (FAB+) Calcd for C13H22O6I: 401.0461; Found: 401.0450. Triethyl 5-Bromopentane-1,1,1-tricarboxylate (30b). Starting from 3.61 g of 1,4-dibromobutane (16.7 mmol) with the same procedure shown in the preparation of 30a, except for the reaction conditions, 80 °C overnight, 2.66 g of 30b was obtained as a colorless oil (86%). 1H NMR (CDCl3) 1.29 (9H, t, J ) 6.9 Hz, CH3), 1.66 (2H, m, -CH2-), 1.90 (2H, m, -CH2-), 2.12 (2H, m, -CH2C(CO2Et)3), 3.41 (2H, t, J ) 6.9 Hz, -CH2Br), 4.26 (6H, q, J ) 6.9 Hz, -OCH2). MS (FAB+) 367 (M + 1). HRMS (FAB+) Calcd for C14H24O679Br: 367.0756; Found: 367.0750. Triethyl 6-Bromohexane-1,1,1-tricarboxylate (30c). Starting from 3.34 g of 1,5-dibromopentane (14.7 mmol) with the same procedure shown in the preparation of 30b, 2.11 g of 30c was obtained as a colorless oil (73%). 1H NMR (CDCl3) 1.29 (9H, t, J ) 6.9 Hz, -CH3), 1.50 (4H, m, -CH2-), 1.88 (2H, m, -CH2-), 2.12 (2H, m, -CH2C(CO2Et)3), 3.41 (2H, t, J ) 6.9 Hz, -CH2Br), 4.27 (6H, q, J ) 6.9 Hz, -OCH2). MS (FAB+) 381 (M + 1). HRMS (FAB+) Calcd for C15H26O679Br: 381.0913; Found: 381.0919. Triethyl 5-Chloro-cis-pent-3-ene-1,1,1-tricarboxylate (30d). Starting from 1.75 g of cis-1,4-dichloro-2-butene (14.0 mmol) with the same procedure shown in the preparation of 30b, 2.40 g of 30d was obtained as a colorless oil (100%). 1H NMR (CDCl3) 1.29 (9H, t, J ) 6.9 Hz, -CH3), 2.95 (2H, d, J ) 6.9 Hz, -CH2C(CO2Et)3), 4.13 (2H, d, J ) 6.9 Hz, -CH2Cl), 4.27 (6H, q, J ) 6.9 Hz, -OCH2), 5.75, 5.82 (2dt, 2H, J ) 10.8, 6.9 Hz, -CHdCH-). MS (FAB+) 321 (M + 1). HRMS (FAB+) Calcd for C14H22O6Cl: 321.1105; Found: 321.1093. Triethyl 5-Bromo-trans-pent-3-ene-1,1,1-tricarboxylate (30e). Starting from 2.99 g of trans-1,4-dibromo-2-butene (14.0 mmol) with the same procedure shown in the preparation of 30b, 1.87 g of 30e was obtained as a colorless oil (73%). 1H NMR (CDCl3) 1.29 (9H, t, J ) 6.9 Hz, -CH3), 2.88 (2H, d, J ) 7.8 Hz, -CH2C(CO2Et)3), 3.91 (2H, d, J ) 7.8 Hz, -CH2Br), 4.26 (6H, q, J ) 6.9 Hz, -OCH2), 5.80, 5.98 (2dt, 2H, J ) 14.7, 7.8 Hz, -CHdCH-). MS (FAB+) 365 (M + 1). HRMS (FAB+) Calcd for C14H22O679Br: 365.0600; Found: 365.0586. Dimethyl 2-[3-(6-Methylamino-purin-9-yl)propyl]malonate (32a). A mixture of 0.373 g of N6-methyladenine (2.5 mmol), 1.1 g of 30a (2.75 mmol), and 0.50 g of dry powdered potassium carbonate (3.6 mmol) in 8 mL of anhydrous DMF was stirred at 60 °C for 24 h. The mixture was filtered while hot, and the filtrate evaporated to dryness under reduced pressure to give a syrupy crude 31a (Rf 0.52, 10:1 CHCl3: MeOH). The crude 31a was dissolved in methanol (4 mL), and sodium methoxide (67.5 mg, 1.25 mmol) was added with stirring. After the mixture was stirred for 1 h at room temperature, 10% HCl was added to raise the pH to 7, and methanol was removed under vacuum. Brine was added, and the mixture was extracted with CH2Cl2 (3 × 30 mL). The organic fractions were combined, dried (anhydrous Na2SO4), filtered, and evaporated. The oily residue was purified by column chromatography (silica gel) eluting with CHCl3 and then 100:1 CHCl3:MeOH to give 0.484 g of pure 32a as a white crystalline solid (60%). Mp 99-103 °C; Rf 0.47 (10:1 CHCl3:

Kim et al. MeOH). 1H NMR (CDCl3) 1.95 (m, 4H, 2×-CH2-), 3.22 (3H, bs, N6-CH3), 3.42 (1H, t, J ) 7.2 Hz, -CH-), 3.73 (6H, s, 2×-OCH3), 4.22 (2H, t, J ) 7.5 Hz, -NCH2-), 5.85 (1H, bs, -NH-), 7.74 (1H, s, H-2), 8.41 (1H, s, H-8). MS (CI NH3) 322 (M + H). HRMS (EI) Calcd for C14H19N5O6: 321.1437; Found: 321.1431. Dimethyl 2-[4-(6-Methylamino-purin-9-yl)butyl]malonate (32b). Starting from 1.01 g of 30b (2.75 mmol) with the same procedure shown in the preparation of 32a, 0.531 g of 32b was obtained (63%). Mp 102-104 °C; Rf 0.44 (10:1 CHCl3: MeOH). 1H NMR (CDCl3) 1.40 (m, 2H, -CH2-), 1.96 (m, 4H, 2×-CH2-), 3.22 (3H, bs, N6-CH3), 3.34 (1H, t, J ) 6.9 Hz, -CH-), 3.73 (6H, s, 2×-OCH3), 4.19 (2H, t, J ) 6.9 Hz, -NCH2-), 5.82 (1H, bs, -NH-), 7.73 (1H, s, H-2), 8.42 (1H, s, H-8). MS (CI NH3) 336 (M + H). HRMS (EI) Calcd for C15H21N5O6: 335.1594; Found: 335.1601. Dimethyl 2-[5-(6-Methylamino-purin-9-yl)pentyl]malonate (32c). Starting from 1.05 g of 30c (2.75 mmol) with the same procedure shown in the preparation of 32a, 0.693 g of 32c was obtained as a crystalline solid (79%). Mp 91-93 °C; Rf 0.44 (10:1 CHCl3:MeOH). 1H NMR (CDCl3) 1.36 (m, 4H, 2×CH2-), 1.89 (m, 4H, 2×-CH2-), 3.21 (3H, bs, N6-CH3), 3.34 (1H, t, J ) 7.8 Hz, -CH-), 3.73 (6H, s, 2×-OCH3), 4.17 (2H, t, J ) 6.6 Hz, -NCH2-), 5.81 (1H, bs, -NH-), 7.72 (1H, s, H-2), 8.42 (1H, s, H-8). MS (CI NH3) 350 (M + H). HRMS (EI) Calcd for C16H23N5O6: 349.1750; Found: 349.1765. Dimethyl 2-[4-(6-Methylamino-purin-9-yl)-cis-but-2enyl]malonate (32d). Starting from 0.88 g of 30d (2.75 mmol) with the same procedure shown in the preparation of 32a, 0.452 g of 32d was obtained as a white solid (57%). Mp 111112 °C; Rf 0.44 (10:1 CHCl3:MeOH). 1H NMR (CDCl3) 2.85 (dd, 2H, J ) 7.8, 6.9 Hz -CH2CHd), 3.21 (3H, bs, N6-CH3), 3.34 (1H, t, J ) 6.9 Hz, -CH-), 3.76 (6H, s, 2×-OCH3), 4.90 (2H, d, J ) 6.9 Hz, -NCH2-), 5.65 (1H, dt, J ) 7.8, 10.8 Hz, -CHd), 5.74 (1H, dt, J ) 6.9, 10.8 Hz, -CHd), 5.85 (1H, bs, -NH-), 7.81 (1H, s, H-2), 8.42 (1H, s, H-8). MS (CI NH3) 334 (M + H). HRMS (EI) Calcd for C15H19N5O6: 333.1437; Found: 333.1445. Dimethyl 2-[4-(6-Methylamino-purin-9-yl)-trans-but-2enyl]malonate (32e). Starting from 1.00 g of 5 (2.75 mmol) with the same procedure shown in the preparation of 32a, 0.20 g of 32e was obtained as a white solid (24%). Mp 114-118 °C; Rf 0.44 (10:1 CHCl3:MeOH). 1H NMR (CDCl3) 2.67 (t, 2H, J ) 6.9 Hz -CH2CHd), 3.21 (3H, bs, N6-CH3), 3.48 (t, 1H, J ) 7.8 Hz, -CH-), 3.71 (6H, s, 2×-OCH3), 4.90 (2H, d, J ) 5.1 Hz, -NCH2-), 5.71, 5.79 (2dt, 2H, J ) 6.0, 15.6 Hz, -CHdCH-), 5.89 (1H, bs, -NH-), 7.71 (1H, s, H-2), 8.42 (1H, s, H-8). MS (CI NH3) 334 (M + H). HRMS (EI) Calcd for C15H19N5O6: 333.1437; Found: 333.1439. 9-[5-Hydroxy-4-(hydroxymethyl)pentyl]-6-methylaminopurine (33a). Starting from 0.172 g of 32a (0.537 mmol) with the same procedure shown in the preparation of 26, 0.110 g of 33a was obtained as white crystals (77%). Mp 156-157 °C; Rf 0.22 (10:1 CHCl3:MeOH). 1H NMR (DMSO-d6) 1.23 (2H, m, CHCH2CH2), 1.47 (1H, m, -CH-), 1.83 (2H, m, -CH2-), 2.96 (3H, bs, N6-CH3), 3.27-3.39 (4H, m, 2×-CH2OH), 4.12 (2H, t, J ) 6.9 Hz, -NCH2-), 4.33 (2H, t, J ) 5.1 Hz, 2×-OH) 7.64 (1H, bs, -NH-), 8.12, 8.22 (2H, 2s, H-2, H-8). MS (CI) 266 (M + 1). HRMS (EI) Calcd for C12H19N5O2: 265.1539; Found: 265.1537. 9-[6-Hydroxy-5-(hydroxymethyl)hexyl]-6-methylaminopurine (33b). Starting from 0.166 g of 32b (0.494 mmol) with the same procedure shown in the preparation of 26, 0.106 g of 33b was obtained as white crystals (77%). Mp 138-140 °C; Rf 0.22 (10:1 CHCl3:MeOH). 1H NMR (DMSO-d6) 1.23 (4H, m, 2×-CH2-), 1.41 (1H, m, -CH-), 1.78 (2H, m, -CH2-), 2.96 (3H, bs, N6-CH3), 3.27-3.39 (4H, m, 2×-CH2OH), 4.14 (2H, t, J ) 6.9 Hz, -NCH2-), 4.29 (2H, t, J ) 6 Hz, 2×-OH) 7.64 (1H, bs, -NH-), 8.13, 8.22 (2H, 2s, H-2, H-8). MS (CI) 280 (M + 1). HRMS (EI) Calcd for C13H21N5O2: 279.1695; Found: 279.1696. 9-[7-Hydroxy-6-(hydroxymethyl)heptyl]-6-methylaminopurine (33c). Starting from 0.186 g of 7 (0.533 mmol) with the same procedure shown in the preparation of 26, 0.114 g of 33c was obtained as white crystals (73%). Mp 139-141 °C; Rf 0.22 (10:1 CHCl3:MeOH). 1H NMR (DMSO-d6) 1.05-1.35 (6H, m, 3x-CH2-), 1.40 (1H, m, -CH-), 1.79 (2H, m, -CH2-), 2.96 (3H, bs, N6-CH3), 3.27-3.39 (4H, m, 2×-CH2OH), 4.13 (2H, t, J )

P2Y1 Receptor Antagonists 6.9 Hz, -NCH2-), 4.26 (2H, t, J ) 5.1 Hz, 2×-OH) 7.64 (1H, bs, -NH-), 8.12, 8.21 (2H, 2s, H-2, H-8). MS (CI) 294 (M + 1). HRMS (EI) Calcd for C14H23N5O2: 293.1852; Found: 293.1863. 9-[6-Hydroxy-5-(hydroxymethyl)-cis-hex-2-enyl]-6methylamino-purine (33d). Starting from 0.167 g of 32d (0.50 mmol) with the same procedure shown in the preparation of 26, 0.101 g of 33d was obtained as white crystals (73%). Mp 127-129 °C; Rf 0.22 (10:1 CH Cl3:MeOH). 1H NMR (DMSO-d6) 1.61 (1H, m, -CH-), 2.44 (2H, t, J ) 6.9 Hz, -CH2CHd), 2.97 (3H, bs, N6-CH3), 3.20-3.43 (4H, m, 2×CH2OH), 4.50 (2H, t, J ) 5.1 Hz, 2×-OH), 4.89 (2H, d, J ) 5.7 Hz, -NCH2-), 5.67 (2H, m, Jcis ) 10.8 Hz, -CHdCH-) 7.66 (1H, bs, -NH-), 8.10, 8.22 (2H, 2s, H-2, H-8). MS (CI) 278 (M + 1). HRMS (EI) Calcd for C13H19N5O2: 277.1539; Found: 277.1549. 9-[6-Hydroxy-5-(hydroxymethyl)-trans-hex-2-enyl]-6methylamino-purine (33e). Starting from 0.104 g of 32e (0.31 mmol) with the same procedure shown in the preparation of 26, 0.066 g of 33e was obtained as white crystals (76%). Mp 115-117 °C; Rf 0.22 (10:1 CHCl3:MeOH). 1H NMR (DMSOd6) 1.51 (1H, m, -CH-), 2.00 (2H, t, J ) 6.0 Hz, -CH2CHd), 2.96 (3H, bs, N6-CH3), 3.26-3.43 (4H, m, 2×-CH2OH), 4.33 (2H, t, J ) 5.4 Hz, 2×-OH), 4.89 (2H, d, J ) 5.2 Hz, -NCH2-), 5.65 (2H, m, -CHdCH-) 7.64 (1H, bs, -NH-), 8.07, 8.22 (2H, 2s, H-2, H-8). MS (CI) 278 (M + 1). HRMS (EI) Calcd for C13H19N5O2: 277.1539; Found: 277.1540. 2-[3-(6-Methylamino-purin-9-yl)-propyl]-propane-1,3bisoxy(dibenzylphosphate) (34a). Starting from 29.2 mg of 33a (0.11 mmol) with the same procedure shown in the preparation of 28, 19 mg of 34a was obtained as a colorless oil (22%). 1H NMR (CDCl3) 1.26 (2H, m, -CH2-), 1.87 (3H, m, -CH2-, -CH-), 3.19 (3H, bs, N6-CH3), 3.87 (4H, dd, J ) 5.7 Hz, 6 Hz, 2×-CH2OP-), 4.03 (2H, t, J ) 6.8 Hz, -NCH2-), 4.95 and 5.02 (8H, 2d, J ) 11.7 Hz, 4×-OCH2Ph), 5.87 (1H, s, -NH-), 7.31 (20H, m, 4×-Ph), 7.62 (1H, s, H-8), 8.39 (1H, s, H-2). 31P NMR (CDCl3) -22.27 (s, 1′-P, 3′-P). MS (FAB+, Cs) 918 (M+ + Cs). HRMS (FAB+) (M + Cs) Calcd for C40H45O8N5P2Cs: 918.1798; Found: 918.1798. 2-[4-(6-Methylamino-purin-9-yl)-butyl]-propane-1,3bisoxy(dibenzylphosphate) (34b). Starting from 29 mg of 33b (0.104 mmol) with the same procedure shown in the preparation of 28, 26 mg of 34b was obtained as a colorless oil (31%). 1H NMR (CDCl3) 1.24 (4H, m, 2×-CH2-), 1.76 (3H, m, -CH2-, -CH-), 3.20 (3H, bs, N6-CH3), 3.88 (4H, m, 2×CH2OP-), 4.06 (2H, t, J ) 6.9 Hz, -NCH2-), 4.90 (8H, m, 4×OCH2Ph), 5.86 (1H, s, -NH-), 7.31 (20H, m, 4×-Ph), 7.67 (1H, s, H-8), 8.41 (1H, s, H-2). 31P NMR (CDCl3) -22.25 (s, 1′-P, 3′-P). MS(FAB+, Cs) 932 (M+ + Cs). HRMS (FAB+) Calcd for C41H47O8N5P2Cs: 932.1954; Found: 932.1979. 2-[5-(6-Methylamino-purin-9-yl)-pentyl]-propane-1,3bisoxy(dibenzylphosphate) (34c). Starting from 30 mg of 33c (0.102 mmol) and 275 mg of tetrabenzyl pyrophosphate (0.511 mmol) with the same procedure shown in the preparation of 28, 20 mg of 34c was obtained as a colorless oil (24%). 1H NMR (CDCl ) 1.22 (6H, m, 3×-CH -), 1.78 (2H, m, -CH -), 3 2 2 1.87 (1H, m, -CH-), 3.21 (3H, bs, N6-CH3), 3.91 (4H, m, 2×CH2OP -), 4.11 (2H, t, J ) 6.9 Hz, -NCH2-), 4.95, 5.02 (4H, 2d, J ) 11.7 Hz, 2×-OCH2Ph), 4.98, 5.00 (4H, 2d, J ) 12.0 Hz, 2×-OCH2Ph), 5.86 (1H, s, -NH-), 7.30 (20H, m, 4×-Ph), 7.70 (1H, s, H-8), 8.42 (1H, s, H-2). 31P NMR (CDCl3) -22.24 (s, 1′-P, 3′-P). MS (FAB+, Cs) 946 (M + Cs). HRMS (FAB+) Calcd for C42H49O8N5P2Cs: 946.2111; Found: 946.2139. 2-[4-(6-Methylamino-purin-9-yl)-cis-but-2-enyl]-propane1,3-bisoxy(dibenzylphosphate) (34d). Starting from 50 mg of 33d (0.18 mmol) and 679 mg of tetrabenzyl pyrophosphate (1.26 mmol) with the same procedure shown in the preparation of 28, 23 mg of 34d was obtained as a colorless oil (16%). 1H NMR (CDCl3) 1.94 (1H, m, -CH-), 2.16 (2H, t, J ) 7.8 Hz, -CH2CHd), 3.21 (3H, bs, N6-CH3), 3.94 (4H, t, J ) 6 Hz, 2×CH2OP-), 4.66 (2H, d, J ) 6.9 Hz, -NCH2-), 5.01 (8H, m, 4×OCH2Ph), 5.49 (1H, dt, J ) 10.8, 7.8 Hz, -CHd), 5.63 (1H, dt, J ) 10.8, 6.9 Hz, -CHd), 5.84 (1H, bs, -NH-), 7.30 (20H, m, 4×-Ph), 7.70, 8.40 (2H, 2s, H-2, H-8). 31P NMR (CDCl3) -22.21 (s, 1′-P, 3′-P). MS (FAB+, Cs) 930 (M + Cs). HRMS (FAB+) Calcd for C41H45O8N5P2Cs: 930.1798; Found: 930.1802.

Journal of Medicinal Chemistry, 2000, Vol. 43, No. 4 753 2-[4-(6-Methylamino-purin-9-yl)-trans-but-2-enyl]-propane-1,3-bisoxy(dibenzylphosphate) (34e). Starting from 44 mg of 33e (0.159 mmol) and 555 mg of tetrabenzyl pyrophosphate (1.11 mmol) with the same procedure shown in the preparation of 34a, 22 mg of 34e was obtained as a colorless oil (17%). 1H NMR (DMSO-d6) 1.85 (1H, m, -CH-), 1.98 (2H, t, J ) 7.8 Hz, -CH2CHd), 3.20 (3H, bs, N6-CH3), 3.88 (4H, m, 2×-CH2OP-), 4.62 (2H, d, J ) 5.7 Hz, -NCH2-), 4.99 (8H, m, 4×-OCH2Ph), 5.48 (1H, dt, J ) 15.6, 6.6 Hz, -CHd), 5.60 (1H, dt, J ) 15.6, 5.7 Hz, -CHd), 5.87 (1H, bs, -NH-), 7.30 (20H, m, 4×-Ph), 7.69, 8.42 (2H, 2s, H-2, H-8). 31P NMR (CDCl3) -22.23 (s, 1′-P, 3′-P). MS (FAB+, Cs) 930 (M+ + Cs). HRMS (FAB+) Calcd for C41H45O8N5P2Cs: 930.1798; Found: 930.1802. 3,5-Di(bromomethyl)-1-nitro-benzene (36). A solution of 1.89 g of 3,5-di(hydroxymethyl)-1-nitrobenzene (35, 10 mmol), 5.25 g of triphenylphosphine (20 mmol), and 6.62 g of carbon tetrabromide (20 mmol) in 50 mL of anhydrous ether was stirred at 25 °C for 12 h under N2 atmosphere. After evaporation, the residue was purified with flash silica gel column chromatography (hex/EtOAc ) 5/1) to give 1.6 g of 36 as a bright yellow solid (52%). 1H NMR (CDCl3) 4.53 (4H, s, 2×CH2Br), 6.83 (1H, s, Ph), 7.76 (1H, s, Ph), 8.20 (1H, s, Ph). MS (EI) (M+) 309. HRMS (EI) Calcd 306.8843; Found 306.8859. Tetramethyl 1-Nitro-benzene-3,5-bis(methylphosphonate) (37). A solution of 1.4 g of 36 (4.53 mmol) in 15 mL of trimethyl phosphite was heated at 80 °C for 6 h. After evaporation, the residue was purified with flash silica gel column chromatography (CHCl3/MeOH ) 30/1) to give 1.57 g of 37 as a white solid (94%). 1H NMR (CDCl3) 3.25 (4H, d, J ) 21.5 Hz, 2×-CH2P-), 3.72 (3H, s, -CH3), 3.73 (3H, s, -CH3), 3.75 (3H, s, -CH3), 3.76 (3H, s, -CH3), 7.28 (1H, s, Ph), 7.60 (1H, s, Ph), 8.06 (1H, s, Ph). 31P NMR (CDCl3) -27.09 (m), 33.48 (m). MS (EI) (M+) 367. HRMS (EI) Calcd 367.0586; Found 367.0592. Tetramethyl 1-Amino-benzene-3,5-bis(methylphosphonate) (38). A solution of 40 mg of 37 (4.53 mmol) and 10 mg of 10% Pd/C in 3 mL of methanol was stirred at 25 °C for 1 h under H2 atmosphere (1 atm). The mixture was filtered through a Celite bed and purified with preparative thin-layer chromatography (CHCl3/MeOH ) 20/1) to give 37 mg of 38 as a white solid (100%). 1H NMR (CDCl3) 3.06 (4H, d, J ) 21.5 Hz, 2×-CH2P-), 3.66 (6H, s, 2×-CH3), 3.70 (6H, s, 2×-CH3), 6.55 (2H, s, Ph), 6.59 (1H, s, Ph). 31P NMR (CDCl3) -27.09 (m), 33.48 (m): with proton decoupling off mode. MS (EI) (M+) 337. HRMS (EI) Calcd 337.0844; Found 337.0845. Ethyl 2-Chloro-6-methylamino-purin-9-yl)-acetate (40). To a suspension of 0.132 g of NaH (3.3 mmol), which was prewashed with 5 mL of hexanes twice, in 2 mL of anhydrous DMF was added 0.55 g of N6-methyl-2-chloro-purine (3 mmol) in 3 mL of DMF at 25 °C under N2 atmosphere. After the mixture was stirred for 30 min, 0.4 mL of ethyl bromoacetate was added, and the stirring was continued for 12 h. After evaporation, the residue was purified with preparative thinlayer chromatography (CHCl3/MeOH ) 25/1) to give 0.66 g of 40 as a white solid (82%). 1H NMR (CDCl3) 1.31 (3H, t, J ) 6.8 Hz, -CH3), 3.20 (3H, bs, -N6-CH3), 4.26 (2H, q, J ) 6.8 Hz, -OCH2-), 4.93 (2H, s, -NCH2CO-), 6.01 (1H, bs, -NH-), 7.78 (1H, s, H-8). MS (EI) (M+) 269. HRMS (EI) Calcd 269.0679; Found 269.0667. 2-Chloro-6-methylamino-9-yl)-acetic Acid (41). Compound 40 (0.33 g, 1.22 mmol) was dissolved in 6 mL of 1 N NaOH with stirring at 25 °C for 1 h. The completion of the hydrolysis was confirmed by HPLC, and the mixture was neutralized to pH 5∼7 with 6 N HCl at 0 °C. A white precipitate was collected by filtration, washed with water, and dried under high vacuum to give 0.245 g of 41 as a white solid (83%). 1H NMR (DMSO-d6) 2.92 (3H, s, -N6-CH3), 4.94 (2H, s, -NCH2CO-), 8.11 (1H, s, H-8). MS (EI) (M+) 241. HRMS (EI) Calcd 241.0366; Found 241.0358. 2-Chloro-9-[(diethanolamino)carboxymethyl]-6-methylamino-purine (42). A mixture of 47 mg of 41 (0.193 mmol), 54 mg of 4-nitrophenol (0.386 mmol), 74 mg of EDAC (0.386 mmol), and 5 mg of DMAP in 1 mL of anhydrous DMF and 1 mL of CH2Cl2 was stirred at 25 °C for 2 h. After evaporation,

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Journal of Medicinal Chemistry, 2000, Vol. 43, No. 4

a solution of 26 mg of diethanolamine (0.251 mmol) in 1 mL of methanol was added, and the reaction mixture was stirred at 25 °C for 12 h. The mixture was concentrated to dryness, and the residue was purified with preparative thin-layer chromatography (CHCl3/MeOH ) 10/1) and crystallized in MeOH:ether (1:2) solution to give 23 mg of 42 as a white solid (36%). 1H NMR (DMSO-d6) 2.92 (3H, bs, N6-CH3), 3.37 (2H, t, J ) 5.9 Hz, N-CH2), 3.48 (2H, t, J ) 5.9 Hz, N-CH2), 3.523.56 (2H, m, CH2OH), 3.63-3.65 (2H, m, CH2OH), 5.17 (2H, s, N-CH2CO), 7.99 (1H, s, H-8), 8.18 (2H, m, OH). MS (EI) (M+) 328. HRMS (EI) Calcd 328.1050; Found 328.1038. 9-Bis(2-dibenzylphosphatoethylamino)-acetyl-2-chloro6-methylamino-purine (43). To a solution of 23 mg of 42 (0.069 mmol) in 2 mL of anhydrous THF was slowly added 0.2 mL of lithium diisopropylamide solution (2.0 M in THF, 0.4 mmol) at -78 °C. After 15 min of stirring, 215 mg of tetrabenzyl pyrophosphate (0.4 mmol) was added and the mixture was stirred for 30-60 min at -78 °C. The reaction mixture was warmed to 0 °C ∼ 25 °C and stirred for additional 12 h. The mixture was concentrated to dryness, and the residue was purified with preparative thin-layer chromatography (CHCl3/MeOH ) 10/1) to give 55 mg of 43 (94%). 1H NMR (CDCl3) 3.16 (3H, s, N6-CH3), 3.37-3.40 (2H, m, CH2), 3.45-3.49 (2H, m, CH2), 3.95-4.07 (4H, m, 2CH2), 4.78 (2H, s, -NCH2-CO), 4.97-5.11 (8H, m, O-CH2), 7.00 (1H, bs, NH), 7.32 (20H, m, C6H5), 7.59 (1H, s, H-8). 31P NMR (CD3Cl) -0.59 (s), -0.72 (s). HRMS (FAB-) (M + Cs) Calcd 981.1310; Found 981.1313. Tetramethyl (2-Chloro-6-methylamino-purin-9-yl)-acetaminophenyl-3′,5′-bis(methylphosphonate) (44). A solution of 24 mg of 41 (0.1 mmol), 34 mg of 38 (0.1 mmol), and 29 mg of EDAC (0.15 mmol) in 3 mL of anhydrous DMF/CH2Cl2 (1/2) was stirred at 25 °C for 12 h. After evaporation, the residue was purified with preparative thin-layer chromatography (CHCl3/MeOH ) 10/1) to give 46 mg of 44 as a white solid (82%). 1H NMR (CDCl3) 2.89 (3H, bs, -N6-CH3), 3.03 (4H, d, J ) 21.5 Hz, 2×-CH2P-), 3.71 (6H, s, 2×-CH3), 3.74 (6H, s, 2×-CH3), 4.97 (2H, s, -NCH2CO-), 6.83 (1H, s, Ph), 7.21 (2H, s, Ph), 7.68 (1H, bs, NH), 7.96 (1H, s, H-8), 9.90 (1H, bs, NH). 31P NMR (CDCl ) 28.96 (m), with proton decoupling off mode. 3 MS (FAB) (M + H) 561. HRMS (FAB) Calcd 561.1183; Found 561.1206. Pharmacological Analyses. P2Y1 receptor promoted stimulation of inositol phosphate formation by adenine nucleotide analogues was measured in turkey erythrocyte membranes as previously described.23,25 The K0.5 values were averaged from 3 to 8 independently determined concentration-effect curves for each compound. Briefly, 1 mL of washed turkey erythrocytes was incubated in inositol-free medium (DMEM; Gibco, Gaithersburg, MD) with 0.5 mCi of 2-[3H]myo-inositol (20 Ci/ mmol; American Radiolabeled Chemicals, Inc., St. Louis, MO) for 18-24 h in a humidified atmosphere of 95% air/5% CO2 at 37 °C. Erythrocyte ghosts were prepared by rapid lysis in hypotonic buffer (5 mM sodium phosphate, pH 7.4, 5 mM MgCl2, 1 mM EGTA) as described.23 Phospholipase C activity was measured in 25 µL of [3H]inositol-labeled ghosts (approximately 175 µg of protein, 200-500000 cpm/assay) in a medium containing 424 µM CaCl2, 0.91 mM MgSO4, 2 mM EGTA, 115 mM KCl, 5 mM KH2PO4, and 10 mM Hepes, pH 7.0. Assays (200 µL final volume) contained 1 µM GTPγS and the indicated concentrations of nucleotide analogues. Ghosts were incubated at 30 °C for 5 min, and total [3H]inositol phosphates were quantitated by anion-exchange chromatography as previously described.23,25 Data Analysis. Agonist potencies were calculated using a four-parameter logistic equation and the GraphPad software package (GraphPad, San Diego, CA). EC50 values (mean ( standard error) represent the concentration at which 50% of the maximal effect is achieved. Relative efficacies (%) were determined by comparison with the effect produced by a maximal effective concentration of 2-MeSADP in the same experiment. Antagonist IC50 values (mean ( standard error) represent the concentration needed to inhibit by 50% the effect elicited

Kim et al. by 30 nM 2-MeSADP. The percent of maximal inhibition is equal to 100 minus the residual fraction of stimulation at the highest antagonist concentration. All concentration-effect curves were repeated in at least three separate experiments carried out with different membrane preparations using duplicate or triplicate assays. Abbreviations: ADP, adenosine 5′-diphosphate; DEAE, diethylaminoethyl; DMAP, 4-(dimethylamino)pyridine; DMF, dimethylformamide; DMSO, dimethyl sulfoxide; EDAC, 1-ethyl3-(3-dimethlyaminopropyl)carbodiimide; FAB, fast atom bombardment (mass spectroscopy); HPLC, high-pressure liquid chromatography; MRS 2179, N6-methyl-2′deoxyadenosine 3′,5′bisphosphate; MS, mass spectroscopy; HRMS, high-resolution mass spectroscopy; LDA, lithium diisoproylamide; 2-MeSADP, 2-methylthioadenosine-5′-diphosphate; TBAP, tetrabutylammonium phosphate; TBPP, tetrabenzylpyrophosphate; THF, tetrahydrofuran; TMS, trimethylsilyl; pTLC, preparative thinlayer chromatography.

Acknowledgment. We thank Gilead Sciences (Foster City, CA), for financial support to E.N. and Mary Furr for technical assistance. We also thank Prof. A. Holy (Inst. of Organic Chemistry and Biochemistry, Academy of Sciences of the Czech Republic), Dr. Haksung Kim, and Dr. An-Hu Li (NIDDK) for helpful discussions. This work was supported by USPHS Grants GM38213 and HL54889. References (1) Fredholm, B. B.; Abbracchio, M. P.; Burnstock, G.; Dubyak, G. R.; Harden, T. K.; Jacobson, K. A.; Schwabe, U.; Williams, M. Toward a revised nomenclature for P1 and P2 receptors. Trends Pharm. Sci. 1997, 18, 79-82. (2) North, R. A.; Barnard, E. A. Nucleotide receptors. Curr. Opin. Neurobiol. 1997, 7, 346-357. (3) Bhagwhat, S. S.; Williams, M. P2 Purine and Pyrimidine Receptors: Emerging superfamilies of G protein and ligandgated ion channel receptors. Eur. J. Med. Chem. 1997, 32, 183193. (4) Fischer, B. Therapeutic applications of ATP-(P2) receptors agonists and antagonists. Exp. Opin. Ther. Patents 1999, 9, 385399. (5) Jacobson, K. A.; Knutsen, L. J. S. P1 and P2 purine and pyrimidine receptors. Handbook of Experimental Pharmacology; Abbracchio, M. P., Williams, M., Eds.; in press. (6) Webb, T. E.; Simon, J.; Krishek, B. J.; Bateson, A. N.; Smart, T. G.; King, B. F.; Burnstock, G.; Barnard, E. A. Cloning and functional expression of a brain G-protein-coupled ATP receptor. Febs Lett 1993, 324, 219-225. (7) Henderson, D. J.; Elliot, D. G.; Smith, G. M.; Webb, T. E.; Dainty, I. A. Cloning and characterization of a bovine P2Y receptor. Biochem. Biophys. Res. Commun. 1995, 212, 648-656. (8) King, B. F.; Townsend-Nicholson, A.; Burnstock, G. Metabotropic receptors for ATP and UTP: exploring the correspondence between native and recombinant nucleotide receptors. Trends Pharmacol. Sci. 1998, 19, 506-514. (9) Boarder, M. R.; Hourani, S. M. O. The regulation of vascular function by P2 receptors: multiple sites and multiple receptors. Trends Pharmacol. Sci. 1998, 19, 99-107. (10) Communi, D.; Paindavoine, P.; Place, G. A.; Parmentier, M.; Boeynaems, J. M. Expression of P2Y receptors in cell lines derived from the human lung. Br. J. Pharmacol. 1999, 127, 562568. (11) Jin, J.; Daniel, J. L.; Kunapuli, S. P. Molecular basis for ADPinduced platelet activation. II. The P2Y1 receptor mediates ADPinduced intracellular calcium mobilization and shape change in platelets. J. Biol. Chem. 1998, 273, 2030-2034. (12) Petit, P.; Hillaire-Buys, D.; Manteghetti, M.; Debrus, S.; Chapal, J.; Loubatieres-Mariani, M. M. Evidence for two different types of P2 receptors stimulating insulin secretion from pancreatic B cell. Br. J. Pharmacol. 1998, 125, 1368-1374. (13) Bolego, C.; Centemeri, C.; Abbracchio, M. P.; Ceruti, S.; Cattabeni, F.; Jacobson, K. A.; Puglisi, L.; Rovati, G. E.; Burnstock, G.; Nicosia, S. Characterization of P2Y receptors involved in UTP- and purine-evoked Ca2+ elevation in mammalian brain astrocytes. Glia, submitted. (14) Boyer, J. L.; Romero-Avila, T.; Schachter, J. B.; Harden, T. K. Identification of competitive antagonists of the P2Y1 receptor. Mol. Pharmacol. 1996, 50, 1323-1329.

P2Y1 Receptor Antagonists (15) Camaioni, E.; Boyer, J. L.; Mohanram, A.; Harden, T. K.; Jacobson, K. A. Deoxyadenosine-bisphosphate derivatives as potent antagonists at P2Y1 receptors. J. Med. Chem. 1998, 41, 183-190. (16) Boyer, J. L.; Mohanram, A.; Camaioni, E.; Jacobson, K. A.; Harden, T. K. Competitive and selective antagonism of P2Y1 receptors by N6-methyl 2′-deoxyadenosine 3′,5′-bisphosphate. Br. J. Pharmacol. 1998, 124, 1-3. (17) Nandanan, E.; Camaioni, E.; Jang, S. Y.; Kim, Y.-C.; Cristalli, G.; Herdewijn, P.; Secrist, J. A.; Tiwari, K. N.; Mohanram, A.; Harden, T. K.; Boyer, J. L.; Jacobson, K. A. Structure activity relationships of bisphosphate nucleotide derivatives as P2Y1 receptor antagonists and partial agonists. J. Med. Chem. 1999, 42, 1625-1638. (18) Nandanan, E.; Jang, S. Y.; Moro, S.; Kim, H.; Siddiqi, M. A.; Russ, P.; Marquez, V.; Busson, R.; Herdewijn, P.; Harden, T. K.; Boyer, J. L.; Jacobson, K. A. Synthesis, biological activity, and molecular modeling of ribose-modified adenosine bisphosphate analogues as P2Y1 receptor ligands. J. Med. Chem. 1999, in press. (19) Moro, S.; Guo, D.; Camaioni, E,; Boyer, J. L.; Harden K. T.; Jacobson, K. A. Human P2Y1 receptor: molecular modeling and site-directed mutagenesis as tools to identify agonist and antagonist recognition sites. J. Med. Chem. 1998, 41, 1456-1466. (20) Freeman, S.; Gardiner, J. M. Acyclic nucleosides as antiviral compounds. Mol. Biotechnol. 1996, 5, 125-137. (21) Martin, J. C.; Dvorak, C. A.; Smee, D. F.; Matthews, T. R.; Verheyden, J. P. H. 9-[(1,3-Dihydroxy-2-propoxy)methyl]guanine: A new potent and selective antiherpes agent. J. Med. Chem. 1983, 26, 759-761. (22) Choudary, B. M.; Geen, G. R.; Kincey, P. M.; Parratt, M. J. A direct approach to the synthesis of famciclovir and penciclovir. Nucleosides Nucleotides, 1996, 15, 981-994. (23) Boyer, J. L.; Downes, C. P.; Harden, T. K. Kinetics of activation of phospholipase C by P2Y purinergic receptor agonists and guanine nucleotides. J. Biol. Chem. 1989, 264, 884-890.

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